The overall goal of this project is the development of proton magnetic resonance spectroscopic imaging (MRSI) techniques and their subsequent application for aiding in the diagnosis and treatment monitoring of patients with tumors. As a noninvasive tool providing unique biochemical information supplemental to conventional imaging, in vivo MRSI has been shown to have a valuable role in the study of cancer. However, significant technical improvements, particularly for the reliable acquisition of volumetric MRSI data from tumors throughout the body, are needed to fully realize the clinical potential of this powerful imaging modality. This proposal is focused on the continued technical development of innovative spectroscopic techniques for the robust and efficient collection, quantification, and display of this information. The techniques will be tested on phantoms, normal volunteers, as well as patients with brain tumors, metastatic neck nodes of squamous cell carcinomas, and breast cancer. In parallel with the continued technical development, we will conduct a focused, well-controlled clinical study comparing the abilities of proton MRSI and FDG PET for differentiating radiation necrosis from recurrent glial tumors.